T-Cell Activation.

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Presentation on theme: "T-Cell Activation."— Presentation transcript:

2 T-Cell ResponseSome types of antigens are recognized by T-cells after being processed by other cells in the immune system, once T-cells recognize an antigenic sequence, they are first activated, then respond to the antigen. T-cells typically respond to intracellular pathogens (such as viruses and intracellular bacteria)

3 T-CellsT-Cells are characterized by a surface receptor, the T-cell receptor (TCR)T-cells are named such because they mature in the thymus (while B-cells mature in bone marrow)T-cells cannot bind antigen directly, and must interact with processed antigenic peptides

4 Types of T-cells There are four different types of T-cellsHelper T-cellsHelper T-Cells are involved in activating and detecting other cells of the immune system and ‘help’ the boost the immune responseCytotoxic T-cellsCytotoxic T-cells kill other cells by releasing granules with cell-death inducing proteinsRegulatory T-cellsRegulatory T-cells regulate the immune response, to prevent an overactivation of the immune systemMemory T-cellsMemory T-cells are used to ‘remember’ specific foreign pathogens

5 T-Cell DevelopmentWhile T-cells originate in the bone marrow, they mature in the thymusIn the thymus, the T-cell undergoes several changes in cell surface molecules, going from double negative to double positive for CD4 and CD8, and ultimately to single positive

6 T-cell ActivationIn order for T-cells to be activated, two different receptors must be engaged: one is TCR, and the other is CD 28Both receptors initiate intracellular signal processes

7 T-Cell Activation, continuedThe TCR and CD 28 receptors activate intracellular proteins, notably tyrosine kinaseInositol phospholipids in the plasma membrane are hydrolizedCellular Ca2+ levels are increased, so that calcineurin can be activatedCalcineurin regulates the transcriptions of genes in the T-cell, and promotes T-cell activation

9 T-Cell ResponseThe response of the T-Cell depends on the type of T-CellCytotoxic T-Cells immediately release perforinand granulysin , which form holes on a target cells plasma membrane, when activatedHelper T-Cells proliferate and release cytokines to stimulate growth of T-cells